How is food digested?

 How is food digested?

When you eat, your digestive system breaks down your food through a process called digestion. Digestion breaks large food molecules (such as fats, carbohydrates, and proteins) into molecules small enough to be absorbed into the bloodstream. These smaller molecules are nutrients.

The bloodstream delivers these nutrients to your cells, along with oxygen (O2) from the air you breathe. Your cells use oxygen to convert the chemical energy in nutrients into energy that cells can use for their activities. In this process, cells also generate carbon dioxide (CO2), heat, and water (H2O).

 food takes through the digestive system.

How is food digested?

Mouth

Digestion begins when food enters the mouth. The mouth can break down food in several ways:

Teeth chew the food into smaller pieces. This is an example of mechanical digestion.

Saliva (spit) mixes with the food and breaks it down with enzymes. This is an example of chemical digestion.

On average, food spends less than 1 minute in the mouth.

Silhouette and cross-section of a person holding a sandwich with bites taken out of it. Illustrated and labeled are the mouth, esophagus and food. There are 3 labeled magnified parts of the sandwich: a yellow square labeled fats, a blue triangle labeled carbohydrates, and a purple diamond labeled proteins. Animation: A piece of the sandwich labeled food starts at the mouth opening and travels into the esophagus.

How is food digested?

Esophagus

Pieces of food from the mouth move down the esophagus. The esophagus doesn’t break down food. It just brings the food to the next part of the digestive system, the stomach.

On average, foo

d spends 5 to 10 seconds in the esophagus.

How is food digested?

Stomach

The stomach continues breaking down the food in several ways:

• Cells lining the stomach produce acid, mucus, and enzymes that help digest food. This is an example of chemical digestion.
• Stomach muscles squeeze the food and mix it with the substances above. This is an example of mechanical digestion.

On average, food spends 2 to 6 hours in the stomach. The food is broken down into large molecules (such as fats, carbohydrates, and proteins), which move on to the small intestine.

How is food digested?

Small Intestine

The small intestine is where most chemical digestion takes place. Enzymes and other substances help break down large food molecules into molecules small enough to be absorbed into the bloodstream:

• Carbohydrates are broken down into monosaccharides.
• Fats are broken down into fatty acids.
• Proteins are broken down into amino acids.

These smaller molecules are nutrients. The bloodstream delivers these nutrients to cells, which can use the nutrients for energy.

On average, food molecules spend 5 to 6 hours in the small intestine.

How is food digested?

Pancreas, Liver and Gallbladder

Two organs, the pancreas and liver, produce substances that help break down food in the small intestine. These substances include:

• enzymes
• bile, which can also be stored in the gallbladder
• buffers

How is food digested?

Large Intestine

Food molecules that are not fully broken down, such as fiber, move from the small intestine into the large intestine. Some of these undigested food molecules are eaten by commensal bacteria. Other undigested food molecules mix with other substances to form feces. Feces move through the large intestine and are eliminated from the body.

On average, undigested food molecules spend 12 hours to several days in the large intestine.

How do nutrients get into our cells?

Silhouette and cross-section of a human torso, illustrating internal organs. Internal organs labeled are the liver, stomach, large intestine, and small intestine. An up arrow appears on the left side of the large intestine and a down arrow appears on the right side. Animation: A feces moves through the large intestine.

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Silhouette and cross-section of a human torso, illustrating internal organs. Internal organs labeled are the liver, stomach, pancreas, gall bladder, large intestine, and small intestine. Three purple arrows labeled Enzymes and buffers point from the liver, pancreas, and gall bladder to the small intestine. Within the small intestine is a cluster of blue triangles, yellow squares, and purple diamonds. One of the blue triangles is magnified and labeled Monosaccharide. One of the yellow squares is magnified and labeled Fatty acid. One of the purple diamonds is magnified and labeled Amino acid.

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Silhouette and cross-section of a human torso, illustrating internal organs and blood vessels. Illustrated and labeled are the liver, stomach, bloodstream, large intestine, and small intestine. A green arrow labeled Nutrients enter the bloodstream points to a cluster of blue triangles, yellow squares, and purple diamonds in the small intestine. One of the blue triangles is magnified and labeled Monosaccharide. One of the yellow squares is magnified and labeled Fatty acid. One of the purple diamonds is magnified and labeled Amino acid. Animation: A large blue triangle, yellow square, and purple diamond enter the intestines from the stomach and then are broken down into smaller yellow squares, blue triangles, and purple diamonds.

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Silhouette and cross-section of a human torso. Illustrated and labeled are the stomach and large intestine. Animation: A cluster of red, yellow, brown, and green circles enters the stomach from the esophagus. The circles are then broken down into yellow squares, blue triangles, and purple diamonds.

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Silhouette and cross-section of a person holding a sandwich with bites taken out of it. Illustrated and labeled are the mouth and esophagus. Animation: A piece of the sandwich travels down the esophagus.